An inverter unit driving an in-vehicle electric motor constitutes a high-voltage system, and a control unit controlling the inverter unit constitutes a low-voltage system insulated from the high-voltage system. When the inverter unit transmits to the control unit a signal representing temperature information on the semiconductor switching elements constituting the inverter unit or a signal representing abnormality information for notifying an abnormality in the semiconductor switching elements, the high-voltage system transmits the signal to the low-voltage system. Since the high-voltage system is insulated from the low-voltage system, the signal transmission from the inverter unit to the control unit is conducted via insulation elements.
PTL 1 describes a configuration for transmitting a signal representing temperature information and a signal representing abnormality information via a common insulation element for the purpose of decreasing the number of insulation elements used.